The outer surface of a piston for a vehicle disc brake undergoes surface treatment to maintain good slidable characteristics with respect to a piston seal and improve operation feeling. Conventionally, there is a known technique for forming a chrome plating layer as this surface treatment. In recent years, there is proposed a technique for forming, on the outer peripheral surface of a piston, a composite plating layer made of nickel-phosphorous alloy including PTFE. This composite plating layer has the characteristics of both polytetrafluoroethylene (PTFE) and electroless nickel and holds good sliding characteristics between the piston and the piston seal (see, for example, PTL 1).